Salmon Raised In Hatcheries Have Different DNA Than Wild Relatives

Juvenile steelhead trout in a natural stream environment are far different than those raised in hatcheries. (Photo : Flickr: Oregon State University)

Seventy percent of salmon sold at the market are farm-raised and believed to be higher in contaminants and unhealthy fats than those caught in their natural habitat. What's worse is diseases can spread easily from farmed fish to their wild relatives. Experts say this could have a devastating impact on wild salmon populations, which have already suffered significantly from human activities such as overfishing and damming.

Attempts have been made to replenish salmon in Oregon and Washington using salmon born in hatcheries. However, the latest study from Oregon State University (OSU) finds fault with this practice.

The study, recently published in Nature Communications proves first-generation hatchery fish have differences in more than 700 of their genes. This includes differences in survival and reproductive abilities that can be passed on to subsequent generations.

"A fish hatchery is a very artificial environment that causes strong natural selection pressures," Michael Blouin, one of the study researchers and a professor of integrative biology in the OSU College of Science, said in a news release. "A concrete box with 50,000 other fish all crowded together and fed pellet food is clearly a lot different than an open stream."

Blouin and his colleagues aren't exactly sure what is causing such genetic selection, but in identifying the 700 different genes researchers hope to learn more about how the fish are adapting to their domesticated lifestyle.

"We observed that a large number of genes were involved in pathways related to wound healing, immunity, and metabolism, and this is consistent with the idea that the earliest stages of domestication may involve adapting to highly crowded conditions," Mark Christie, lead author of the study, added in the release.

Aside from crowding, hatchery fish regularly suffer more injuries and are more susceptible to disease outbreaks. Since the genetic changes are substantial and rapid, researchers say it is clearly evolution at work. However, in this case, it does not take multiple generations or long periods of time for the adaptations to take effect in subsequent generations.

"We expected hatcheries to have a genetic impact," Blouin said in the university's release. "However, the large amount of change we observed at the DNA level was really amazing. This was a surprising result."

With a better understanding of how genetic changes arise in a hatchery environment, researchers hope to improve the way fish are raised so that they are more similar to their wild counterparts.